<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            /* flex-direction: column; */
            display: flex;

            height: 300px;
            border: 1px solid red;

        }
        .box div{
            background-color: pink;

        }
        .box div:nth-child(1){
            width: 100px;
        }
        .box div:nth-child(2){
            flex: 1;
        }
        .box div:nth-child(3){
            flex: 2;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="item">1</div>
        <div class="item">2</div>
        <div class="item">3</div>
    </div>
</body>
</html>